The oil is obtained from a process stemming from the gas combustion process used for bituminous shales. This technique allows one to obtain a yield in light products higher than those from the TOSCO and TACIUK processes, already used in the case of the Bemolanga sandstone which is studied here. The oil can either be used as a gas oil-since the simulated distillation shows that it does not contain really vacuum residues-or be treated by a further hydrogenation. After a chromatographic separation in saturated, olefinic and aromatic fractions, the oil was analyzed by NMR and FIMS techniques. The comparison of the results with those obtained for the initial bitumen shows that the process led to the total combustion of the asphaltenes and that the other fractions were changed in lighter fractions because of the opening of the naphthenic rings and the breaking of the lateral side-chains.